Wow, thanks for the support!
I've thought about this, I guess most of what I've done can be done programmatically, but I don't think I'm capable enough. I know Grappigegovert's GDB converter includes the UV texture mapping, but I don't know much about how that works, whether it links to the specific texture files or if it does that anywhere else in the game.
Let me set this straight. I didn't say I was remaking the game, or porting it. This was literally an exercise, and I thought people here might find it interesting, one because I'm using tools developed by members here who might see this, and two because it might be useful for anyone's own projects. I've not added any gameplay elements, and I hadn't really thought about it. Plus the physics was pretty dodgy in the original. I loved it, but it was definitely dodgy.
Well, if I understand correctly Unity isn't really for modelling. You could modify the extracted models, but I don't think there's a way to get the models back in (edit: yet). I'm pretty sure there's talk about it in the Modding section of the forums somewhere.